Weatherproofing for Northern Climates

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Overview

The enduring strength, beauty and performance of a brick wall assembly is critically dependant on three components: design, workmanship and materials. If even one of these factors has not been diligently applied, integrity of the wall assembly is compromised.

The single most important factor to be understood and designed for in the severe northern climate is moisture control. Seldom does failure of a brick wall assembly occur without the presence of an excessive moisture load. Excessive is defined as being more moisture than can dry out of the assembly before that assembly freezes due to ambient temperature conditions. The trapped moisture will freeze and thaw and may cause deterioration known as spalling , in which part of the brick surface may break away.

This Technical Note is applicable to those areas subjected to severe winter weather, including Canada and the northern states of the USA.

Examples of Extra Severe Weathering Conditions:

• Houses and buildings built within the spray zone of lakes
• Buildings constructed in open areas with little or no protection from the wind by other buildings or trees
• Upper floors of high rise buildings

It should be noted that certain parts of masonry structures are more vulnerable to the weather than others. These include parapet walls surmounting multi-storey buildings, freestanding walls, chimneys and walls put in contact with the grade level. In these adverse conditions, it is even more critical to ensure the correct use of materials, details and workmanship.

Chimneys

The two most critical components of chimney construction are workmanship and a proper chimney cap. (See Fig. A for proper chimney cap details.)
Ensure that the chimney cap installed has an overhang of no less than 50mm (2"), and a drip groove (as shown in Fig. A) to shed water past the plane of the four chimney walls. Ensure that all joints are properly caulked.

Note: The through wall flashing detail shown in Fig. A applies to all masonry walls which traverse the roof line. i.e. where an exterior wall (or chimney) above the roofline is supported below the roofline by masonry, through wall flashing must be installed at the roofline to direct water to the exterior.

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